1. Technical Field
The present disclosure relates generally to the production of acetic anhydride and more particularly, to apparatus and methods enhancing the production of acetic anhydride. More specifically, the disclosure relates to the reduction of mass transfer limitations of apparatus and methods for the production of acetic anhydride.
2. Background of the Invention
Acetic anhydride is an industrial chemical reagent, widely used in organic synthesis. Furthermore, large quantities are used, for example, in the manufacture of cellulose acetate as well as other commercially significant acetylations. It has commonly been produced on an industrial scale by the reaction of ketene and acetic acid. Conventionally processes for preparing acetic anhydride have been disclosed in U.S. Pat. Nos. 4,115,444; 4,252,983; 4,333,885; 4,519,956; 4,563,309; and 5,488,143.
U.S. Pat. No. 7,199,263 describes a process for co-production of acetic anhydride and acetate co-production. The production of acetic anhydride by the ketene process is conventionally known. The method comprises the thermal decomposition of acetic acid at high temperatures utilizing, for example, triethyl phosphate dehydration catalyst to produce ketene (1) which is subsequently reacted with excess acetic acid to obtain acetic anhydride (2):CH3COOH→H2C═C═O+H2O  (1)H2C═C═O+CH3COOH→O═CCH3OCH3C═O  (2)
Reaction (1) is carried out at low pressure and elevated temperature, typically in excess of 700° C. Catalyst in the product stream may be neutralized with ammonia. The process is widely employed however, it is capital intensive. For efficient acetic anhydride production, water generated in reaction (1) is removed and acetic acid is recovered. Due to the quantity of water, 1 mole of water per mole of ketene, weak acid recovery adversely impacts operating energy costs.
Accordingly, there is a need in the industry for improved processes for the production of acetic anhydride whereby water removal and acid recovery are increased, so that production of acetic anhydride is more commercially feasible.